1. Field of the Invention:
The present invention relates to a curved pipe manufacturing method and an apparatus for carrying out the same in which a straight pipe of stainless steel or the like is pressed into a fixed die having a curved cavity of a circular arc shape to form a curved pipe.
2. Description of the Prior Art:
Japanese Pat. Publication No. 54-23677 discloses a curved pipe manufacturing method employing an apparatus as illustrated in FIG. 4, invented by the inventor of the present invention. According to this known curved pipe manufacturing method, a work, namely, a straight pipe 5, is pressed with a presser rod 15 into a curved space conforming to the shape of a curved pipe to be formed, defined by a curved cavity 4 formed in a fixed die 1 to extending from the entrance opening 2 to the exit opening 3 of the fixed die 1. A curved mandrel 7 is secured to a movable block 6 so as to be inserted into and to be extracted from the curved cavity 4 of the fixed die 1, through the exit opening 3 of the fixed die 1 to form a curved pipe. Then the movable block 6 is turned to extract the mandrel 7 from the fixed die 1, and then the movable block 6 is turned further to push out the curved pipe from the fixed die 1 with an ejecting rod 8 attached to the movable block 6 opposite to the mandrel 7.
Inasmuch as the known curved pipe manufacturing method employs the mandrel 7 fixed to one end of the movable block 6 and the ejecting rod 8 at the other end of the movable block, the work, pressedly inserted through the entrance opening 2, is extracted from the exit opening 3 after it was subject to the curved pipe forming process, the known curved pipe manufacturing method has the following problems.
(1) Space is required for inserting the work into and extracting the work from both ends of the fixed die 1 (at the side of the entrance opening 2 and the exit opening 3 of the curved cavity 4) so that the apparatus necessarily becomes of large size.
(2) Since the direction for inserting the mandrel 7 is opposed to that for inserting the ejecting rod 8, the angle of rotation of the movable block 6 is greater than 180.degree. which necessitates a device for rotatively driving the movable block 6 to be of large size.